On 16 October 1966, 60 years before this post, one of the strangest aircraft ever built made its first flight. The KM was 92 metres long, carried ten jet engines and was designed to fly only a few metres above the water. Wikipedia says it was then the largest and heaviest aircraft in the world until 1988.

What it was

The KM was an ekranoplan, a wing-in-ground-effect machine. Instead of climbing to altitude, it flew close to the surface, where the cushion of high-pressure air trapped between wing and water gives extra lift. Migflug's history of the aircraft says it flew within about a wingspan of the surface and cruised at up to 500 km/h, a few metres above the Caspian.

The designer was Rostislav Alexeyev, chief designer at the Central Hydrofoil Design Bureau, with V. Efimov as lead engineer, according to Wikipedia. It was built at the Red Sormovo plant in Gorky, now Nizhny Novgorod. The name KM stands for Korabl Maket, which Wikipedia renders as "Ship-maquette". "Caspian Sea Monster" is the English nickname that stuck.

The numbers

Wikipedia's specifications give a length of 92 metres, a wingspan of 37.6 metres and a maximum take-off weight of 544 tonnes. Migflug also gives about 544 tonnes. Euroavia lists 544,000 kg in one place and 494 tons in another, so I would treat the exact weight with care and lean on the 544-tonne figure that two of the three sources share.

The engine arrangement is the oddest part. Wikipedia says there were ten Dobrynin turbojets: two mounted at the tail and eight on the canard, the small forward wing. Wikipedia and Migflug both say the eight forward engines were shut off after take-off, leaving the two at the back to cruise.

The first flight

The date is solid. Wikipedia, Euroavia and Migflug all give 16 October 1966, and Wikipedia says it was flown by Vladimir Loginov and Alexeyev himself. Wikipedia's article on Alexeyev notes that this was unusual, since designers rarely flew their own aircraft.

A record that lasted

Wikipedia says the KM was the largest and heaviest aircraft in the world from 1966 until 1988, when the Antonov An-225 Mriya first flew. Migflug says the same.

What I have not been able to confirm

I have not found a photograph of the KM that I can use under a free licence, so this post uses text and a drawing instead. Accounts of how the "Caspian Sea Monster" nickname started also vary between sources, so I have left that out.

Why it is worth a look

It is easy to treat the KM as a curiosity, and it is one. The idea behind it is simple to say: stay low and let the air trapped under the wing do the lifting. Making that work in a 544-tonne aircraft with ten engines is what makes it such an engineering oddity.

If you could pick one oddity from aviation history to see in the flesh, would it be this one?

Sources

  • Wikipedia, "Caspian Sea Monster": https://en.wikipedia.org/wiki/Caspian_Sea_Monster
  • Wikipedia, "Rostislav Alexeyev": https://en.wikipedia.org/wiki/Rostislav_Alexeyev
  • Migflug, "The Caspian Sea Monster That Spooked the CIA": https://migflug.com/jetflights/caspian-sea-monster-ekranoplan/
  • Euroavia, "The Caspian Sea Monster", 16 February 2021: https://blog.euroavia.eu/2021/02/16/the-caspian-sea-monster/
  • Drawing: Kilyann Le Hen, "KM 3-view.svg", CC BY 4.0, via Wikimedia Commons